Increasing nitrogen use efficiency and energy ratios of biofuel grasses with nitrogen fixing bacteria

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Two of the greatest challenges to humanity during the 21st century will be energy supply and climate change. Biofuels are where these two challenges come together. One of the most expensive, both energetically and economically, inputs into crop production is nitrogen fertilizer. Reductions in nitrogen fertilizer applications will also reduce emissions of the potent greenhouse gas nitrous oxide, associated with N fertilizer applications. Among the potential crops utilizable for the production of cellulosic biomass for biofuel production are the fast growing grasses. The three for these probably most appropriate to Canadian conditions are Miscanthus, switchgrass and reed canarygrass. The first two can be produced in southern Canada and the latter further north. Under Canadian conditions all three can produce yields in excess of 10 t ha-1 of processable biomass. One way to reduce nitrogen fertilizer requirements is to rely on biological nitrogen fixation by rhizobacteria living near, on or in crop roots. We propose to isolate free-living nitrogen-fixing rhizobacteria from stands of Miscanthus, switchgrass and reed canarygrass stands that have been grown with little or no nitrogen fertilizer for at least 15 years. Isolated strains will be screened for ability to fix nitrogen. We will test these strains along several well known diazotrophic rhizobacteria, on Miscanthus, switchgrass and reed canarygrass under controlled environment conditions and the best two for each crop will be identified. These strains will be characterized and their taxonomic status determined through 16S rRNA sequence data. The best strains will then be tested under field conditions, first on stands of switch grass already established at the Macdonald Campus agronomy research station and then on purpose grown stands of all three crops for 2 seasons. The data will be used to determine crop productivity, nitrogen use efficiency and energy ratio. The development of biofuel crop production systems that require little nitrogen fertilizer will improve both the economics and energetics of biofuel production. This will facilitate the development of the biofuels energy sector, will reduce greenhouse gas emissions and lead to rural renewal.